1. Field of the Invention
The present invention relates to an intravascular stent particularly intended for angioplasty.
This type of prosthesis is known as, for example, a PALMAZ stent (registered trademark) marketed by JOHNSON & JOHNSON and is described in the article "Introduction to intravascular stents" by Richard A. SCHATZ published in "CARDIOLOGY CLINICS" Vol. 6 No. 3 August 1988". These stents are made up of a material which allows for radial expansion with a balloon probe. They have an open-work casing, for example in diamond shape, which enables such expansion to take place and to increase the free arterial surface of the metal after implanting. They are intended to support the vascular wall.
In most cases this type of stent is satisfactory. However, when it is implanted near a bifurcation, its end may sometimes project into the medullary canal of the unaffected branch causing a disturbance to blood flow.
It has nevertheless come to light that stents placed near a branch point undergo irregular, often incomplete endothelialisation, unlike implants placed on straight vessels such as femoral vessels.
Surgeons consider that stents must not prolapse and therefore implant them slightly behind the bifurcation which means that the affected area is not fully covered even though it often extends into part of the other branch.
2. Description of Related Art
To overcome this drawback, in an article entitled "Aortic bifurcation stenosis: treatment with intravascular stents" published in "RADIOLOGY-JVIR, Vol. 2, No. 3, August 1991, pp 319-323, it was proposed to implant a stent in both stenosed branches and to bring the ends of both stents parallel to each other into the common branch of the vessels. With this solution it is possible, it is true, to cover all affected areas and to maintain substantially laminar blood flow, but it has the disadvantage of substantially reducing the effective section of the common branch and can only be used for vessels that are sufficiently wide.
French patent FR2678508 also proposed a stent comprising an elongated reinforcement which fits inside the inner wall of the vessel to be reinforced. In order to achieve continuous junctions, especially at bifurcations, at least two devices are provided comprising self-locking spirals with which continuous connections can be made.
Another French patent published under number FR2671280 describes a stent made up of several modular units each comprising flexible, elastic longitudinal axes connected together by enmeshed "V" fibres giving a fishbone appearance; 2, 3 or more units connected together longitudinally form an elastic cylinder. This device may be passed into an artery with a catheter and an application device which is used to stretch the open-work cylinder to reduce its diameter and then to allow it to resume its initial shape.
These types of stent do not solve the problem of the invention and are also difficult and costly to manufacture.